Stable-Phase Diagram of the Quaternary Water–Salt System K+, Rb+, Cs+//SO42––H2O at T = 323.2 K
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Abstract:
The stable-phase equilibria of the aqueous quaternary system K+, Rb+, Cs+//SO42––H2O was investigated at T = 323.2 K using the isothermal dissolution equilibrium method. The solubility, density, and refractive index of equilibrium solutions were determined using the chemical/instrument analysis method, the specific gravity bottle method, and the WYA Abbe refractometer, respectively. The solid phases were identified by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results reveal that besides three single salts (K2SO4, Rb2SO4, and Cs2SO4), three complete solid solutions are formed in this system at 323.2 K, namely, [(Kx, Rb1–x)2SO4], [(Kx, Cs1–x)2SO4], and [(Rbx, Cs1–x)2SO4], increasing the difficulty of separation potassium from the solution composed of rubidium, cesium, and sulfate. The stable-phase diagram of the quaternary system K+, Rb+, Cs+//SO42––H2O at T = 323.2 K consists of four invariant points, nine univariant curves, and six crystallization regions. The sequence of the size of the salt crystal region is [(Kx, Rb1–x)2SO4] > [(Kx, Cs1–x)2SO4] > K2SO4 > [(Rbx, Cs1–x)2SO4] > Rb2SO4 > Cs2SO4. The phase diagrams at different temperatures (T = 298.2 K and T = 323.2 K) show that temperature is an important factor affecting salt crystallization, especially for the solid solution. As the temperature increases, the crystallization region of [(Kx, Cs1–x)2SO4] conspicuously decreases, whereas the crystallization regions of [(Kx, Rb1–x)2SO4] and [(Rbx, Cs1–x)2SO4] increase slightly.Keywords:
Rubidium
Double salt
Isothermal process
Key phase diagram experiments for the CaO–CaF2 system were conducted using an equilibration and quenching technique and thermal analysis. Equilibration and quenching experiments using sealed Pt capsules followed by FE-SEM EDS compositional analysis and XRD phase analysis were performed to determine the CaO and CaF2 liquidii and the solubility of CaO in solid CaF2. Thermal analyses with DSC and TGA were used to determine the temperatures of the eutectic and the α- to β-CaF2 polymorphic transition. For the first time, noticeable solubility of CaO in α- and β-CaF2 solids is observed above 1000°C. The maximum solubility of CaO in solid CaF2 is about 5 mol% at the eutectic temperature (about 1361°C) while no solubility of CaF2 in solid CaO is detected. Based on the thermodynamic optimization using the present CaO and CaF2 liquidii and the eutectic temperature measurements, it is concluded that the CaO–CaF2 binary is a simple eutectic system with the eutectic reaction L(CaO = 15 mol%) → CaO(pure solid) + CaF2(solid solution with CaO = 5 mol%) at 1361°C. The α- to β-CaF2 polymorphic transition is located at about 1146°C and the melting point of CaF2 at 1420°C.
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In view of the composition characteristics of lithium, calcium, and bromine rich in Nanyishan oilfield water of the Qaidam Basin, Qinghai Province, the phase equilibrium relationships of quaternary system LiBr–NaBr–KBr–H2O and its ternary subsystems LiBr–NaBr–H2O and LiBr–KBr–H2O at 348.15 K were studied by the isothermal solution equilibrium method, and the equilibrium solid-phase crystallization regions and composition of each invariant point in each system were determined. The results show that there is no complex salt or solid solution in ternary systems LiBr–NaBr–H2O and LiBr–KBr–H2O at 348.15 K, and the phase diagram contains only one invariant point, two isothermal univariate curves, and two equilibrium solid-phase crystallization regions. The quaternary system LiBr–NaBr–KBr–H2O also has no formation of complex salt or solid solution, and the phase diagram contains only one invariant point, three isothermal univariate curves, and three equilibrium solid-phase crystallization regions. Meanwhile, the phase equilibrium relationships and change laws of each component of the above-mentioned systems at different temperatures were compared and discussed.
Isothermal process
Double salt
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Powder Diffraction
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Isothermal process
Ternary numeral system
Section (typography)
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Isothermal process
Ternary numeral system
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The isothermal solubilities and properties (density,pH value and electrical conductivity) of solution in the quarternary system Na2SO4-Na2B4O7-Na2CO3-H2O at 298K were studied by the isothermal solution equilibrium method.It showed that the system is a type of simple common saturation,and without complex salt and solid solution.Based on the solubility data,the phase diagram of the quarternary system was plotted.It consists of one eutectic point(E),three univariant curves(E1-E,E2-E,E3-E) and three solid crystallization fields.The phase equilibrium solids are Na2SO4·10H2O,Na2B4O7·10H2O and Na2CO3·10H2O.The results of experiments for this solution were discussed simply.
Isothermal process
Saturation (graph theory)
Double salt
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The characteristics of local phase diagram in WC-(Ni-Fe)pseudo binary system were studied by means of optical microscope,SEM,X-ray diffraction and thermal-analysis.The maximum solubility and the solubility at room temperature of WC in γphase were also measured.The results show that WC-(Ni-Fe)pseudo binary system is still a typical WC-(Ni-Fe)eutectic phase diagram.The eutectic temperature is 1419℃.The solubility of WC in γ phase varies with temperature.The maximum solubility at eutectic temperature is 11.2% and the solubility at room temperature is 9.01%.
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Solid solubility
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